Non-hormonal vaginal contraceptive

ABSTRACT

The present invention relates to a non-hormonal, biocompatible, and biodegradable intravaginal device for the delivery of spermiostatic, spermicidal and anti-infectious agents. The present invention also relates to methods of contraception using such a device, as well as the prevention and treatment of sexually transmitted diseases and vaginal infections through the application of the device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of currently pending U.S. patentapplication Ser. No. 10/362,068, filed on Jul. 31, 2003, titled“NON-HORMONAL VAGINAL CONTRACEPTIVE,” which is a National Stage filingof International Application No. PCT/US01/26475 filed Aug. 24, 2001,which claims the benefit of U.S. Provisional Patent Application Ser. No.60/227,740, filed Aug. 24, 2000, the entire contents of all of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a non-hormonal biodegradableintravaginal device for the delivery of spermiostatic, spermicidal, andanti-infectious agents, and methods for contraception and the preventionand treatment of infection using such a device.

BACKGROUND OF THE INVENTION

Currently, intravaginal barrier and intrauterine contraceptive devices,with or without hormones, are available to inhibit ovulation and toprevent sperm migration into the cervix and fertilization (Roy, “Statusof Research and Development of Vaginal Contraceptive Rings as FertilityControl Method in the Female,” Research Frontiers in FertilityRegulation, Family Health Network International Bulletin 2(4):1-10(2000). A literature search for non-hormonal, non-toxic, andnon-invasive contraceptive agents, as well as the anti-microbial andanti-viral (U.S. Pat. No. 5,595,980 to Brode) agents revealed that metalions and their derivatives, such as calcium chloride, sodium chloride,magnesium chloride, copper, and ferrous sulfate act as spermicidaland/or spermiostatic agents (U.S. Pat. No. 4,959,216 to Daunter). Coppersulfate has been used in intrauterine devices (“IUDs”) as a spermicidalagent. It is known that sulfhydryl groups are essential components ofcertain vital enzymes necessary for stability of the sperm. Thecopper-based agents are toxic due to their sulfhydryl binding propertiesand thus cause a direct deleterious effect on sperm. Copper alsoinfluences midcycle human cervical mucus by causing lysis of the mucusmaterial, changing the physico-chemical properties of the mucusresulting in a decrease in sperm penetration (Shoham et al., “Influenceof Different Copper Wires on Human Sperm Penetration Into BovineCervical Mucus,” In Vitro Contraception 36(3):327-34 (1987)).

Diveley (U.S. Pat. No. 3,950,366) tested metal salts of1,1,5,5-tetrasubtituted-dithiobiurets as spermiostatic agents. Lightmetals such as sodium and potassium, alkaline earth metals such ascalcium and barium, and heavy metals such as zinc, cadmium, tin,mercury, copper, nickel, chromium, iron, manganese, and cobalt, givenorally as chelates, have been shown to form dithiobiuret salts, whichact as contraceptive and pregnancy terminators. Sawan et al., (U.S. Pat.No. 5,224,493) showed that insoluble, inorganic metallic salts andoxides of silver, magnesium, zinc, copper, cadmium or arsenic can beused as anti-inflammatory agents. Brode used benzylalkonium chloride,octoxynol-9, nonoxyl-9, ricinoleic acid, and phenol mercury acetates asspermicides delivered via hydrophobically modified polysaccharides as apolymeric delivery system to reduce the potential for infection andsexually transmitted diseases (STD) (U.S. Pat. No. 5,595,980 to Brode).

Cellulose-based vehicles consisting of hydroxyethyl cellulose andhydroxyethyl methyl cellulose, or mixtures thereof, or optionally acosmetic ingredient selected from the group consisting of water, ethylalcohol, isopropyl alcohol, glycerin, glycerol, propylene glycol, andsorbitol, have also been used as delivery systems. Typical forms ofdelivery systems used vaginally include creams, lotions, gels, foams,sponges, suppositories, and films. Daunter usedCu-ethylenediaminetetraac-etic acid/L-ascorbic acid, neuraminidase, andasialofetuin as fertility preventing agents which can be delivered viapolyurethane or polyvinyl acetate discs (U.S. Pat. No. 4,959,216 toDaunter). The first two agents act on the cervical mucus to change itfrom the open cellular structure found at midcycle of the menstrualperiod to the closed structure that forms an impenetrable barrier forsperm. An ethylene vinyl acetate copolymer has also been used as acomponent of the matrix for the intravaginal device. Albumin increasesthe viscosity of the cervical mucus by diminishing the effect on ferningand spinnbarkeit. Albumin, dextran, and vinyl acetate were found toaffect mucus spinnbarkeit due to the polymerization of the mucousglycoprotein, resulting in an increase in the viscosity of the cervicalmucus. The spermicidal effect of certain devices was also based on theirability to change the vaginal pH to become more acidic (Olmsted et al.,“The Rate at Which Human Sperm Are Immobilized and Killed by MildAcidity,” Fertility And Sterility 73(4):687-693 (2000).

The success rate of a contraceptive depends not only upon the efficacyof the contraceptive method, but also upon the user's preference,reversibility, convenience, and compliance. Besides pregnancy, sexualrelations can also transmit infection. It is thus beneficial that thedesign of new contraceptive devices should also consider the option ofprotecting women against transmission of sexually transmitted diseases(STDs) as well as against pregnancy. Hormone-based contraceptives havelong been identified as posing an adverse metabolic risk, and are, infact, contraindicated for individuals with a variety of cardiovascularconditions. Therefore, new contraceptive devices must be free of toxiccompounds and hormones. In addition, a contraceptive method should allowwomen to use the method themselves in conjunction with normal managementof their menstrual cycle as a tampon exchange month after month, thusenhancing the quality of life. However, a controlled releasebiodegradable delivery vehicle of bioactive agents for contraceptionover extended periods has not been developed thus far.

There is a pressing need to develop a non-hormonal, biocompatible,non-invasive, cost-effective, biodegradable, and convenient barrierdevice to prevent pregnancy and infection. The present invention isdirected to overcoming these and other deficiencies in the art.

SUMMARY OF THE INVENTION

The present invention relates to a non-hormonal, biocompatibleintravaginal device for delivery of spermiostatic and/or spermicidal,and/or anti-infective agents. This device is a flexible structureimpregnated with an effective concentration of biocompatiblespermiostatic agents and/or spermicidal agents, and/or anti-infectiveagents.

The present invention also relates to methods of contraception. Thismethod involves introducing a device according the present inventioninto the vagina of a female mammal.

The present invention also relates to a method of preventing infectionin mammals. This method involves introducing the device of the presentinvention present invention into the vagina of a female mammal.

The present invention also relates to a method of treating vaginalinfections in mammals. This method involves introducing the device ofthe present invention into the vagina of a female mammal.

Contraceptives prevent unwanted pregnancies and provide better familyplanning and health care. Convenience, safety, efficacy, and cost, aswell as the quality of life, are usually the concerns in choosing acontraceptive. The present invention meets these needs by providing anon-hormonal, biodegradable, and biocompatible intravaginal device thatacts locally, avoids a systemic route to deliver contraceptive andanti-infection agents, and is easy to use. The flexibility of thedevice, and the fact that, unlike contraceptive devices such as thecervical cap, the device of the present invention does not need to becarefully positioned, make self-insertion of the device simple.Furthermore, the device of the present invention can be used withoutdetection by a male partner, thus it does not interfere with sexualactivity. Despite the fact that the device slowly degrades over thecourse of efficacy, there is no slippage problem. The device is designedto be inserted by a woman at the very end of her menstrual period, adate which most women are sensitive to and respond to as a matter ofcourse. Thus, usage of the device is not necessarily related toanticipated sexual relations, but rather, to normal post-menstrualhygiene which she attends to ordinarily and regularly. Since both thecore and the sheath are composed of biodegradable materials, the devicedoes not need to be removed at the end of its period of effectiveness.Therefore, the delivery device of the present invention allows for asimple, once monthly insertion while providing contraceptive andanti-infective protection for up to 28 days duration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-C show some of the physical configurations possible for thedevice of the present invention. FIG. 1A shows the device as a ring witha smooth outer surface. FIG. 1B shows the device as a ring with a highlyconvoluted outer surface. FIG. 1C shows the device as a ring with amoderately convoluted outer surface.

FIG. 2 shows the effects of calcium chloride (CaCl.sub.2), magnesiumchloride (MgCl.sub.2), and ferrous sulfate (FeSo.sub.4) on spermmotility.

FIG. 3 shows the effects of copper sulfate and dihydrate ferrousgluconate on sperm motility in vitro.

FIG. 4 shows the effects of 12.5 mM ferrous gluconate on sperm motilityin the presence of increasing concentration of albumin, with and without2.5% dextran added.

FIG. 5 shows the daily release of ferrous gluconate from matrix Sample Aand the spermiostatic effect (in seconds) over a 20 day time course.

FIG. 6 shows the daily release of ferrous gluconate from matrix Sample Band the spermiostatic effect (in seconds) over a 20 day time course.

FIG. 7 shows the daily release of ferrous gluconate from matrix Sample Cand the spermiostatic effect (in seconds) over a 16 day time course.

FIG. 8 shows the daily release of ferrous gluconate from matrix Sample Dand the spermiostatic effect (in seconds) over a 16 day time course.

FIG. 9 shows the daily release of ferrous gluconate from hydrogel matrixSample DA over a 22 day time course.

FIG. 10 shows the daily release of ascorbic acid from hydrogel matrix DAover a 21 day time course.

FIG. 11 shows the spermiostatic effect of the daily eluates of hydrogelmatrix Sample DA over an 11 day time course.

FIG. 12 shows the pH of the daily eluates of the hydrogel matrix SampleDA over an 11 day time course.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a non-hormonal biocompatibleintravaginal device for delivery of spermiostatic and/or spermicidal,and/or anti-infective agents. This device is a flexible structure, forexample, a ring or a modification of a ring, impregnated with aneffective concentration of biocompatible spermiostatic agents and/orspermicidal agents, and/or anti-infective agents. Non-hormonal as usedherein refers to the use of materials in the device of the presentinvention which do not include estrogen, progesterone, other steroids,or derivatives thereof, which are systemic in action. In contrast, thematerials suitable for the present invention are non-hormonal,non-steroidal, and act locally at the site of insertion. The basicdesign of the delivery vehicle of the present invention is a hydrogelcore-sheath configuration made of biocompatible and biodegradablepolymers, which may be either natural and/or synthetic. The objective ofthe core-sheath configuration is to facilitate the sustained release ofimpregnated agents for up to a 28-day period. The hydrogel core conceptutilizes recent advances in biodegradable three-dimensional hydrogelnetwork biomaterials. Biodegradable hydrogels as a delivery vehicle havethe advantage of being environmentally friendly to the human body (dueto their biodegradability) and of providing more predictable, controlledrelease of the impregnated drugs. Hydrogels as delivery vehicles havereceived significant attention for use as medical implants. Hydrogelsare of special interest in biological environments since they have ahigh water content as is found in body tissue and are highlybiocompatible. Hydrogels and natural biological gels have hydrodynamicproperties similar to that of cells and tissues. Hydrogels minimizemechanical and frictional irritation to the surrounding tissue becauseof their soft and compliant nature. Therefore, hydrogels provide a farmore user-friendly delivery vehicle than the relatively hydrophobiccarriers like silicone, or vinyl acetate.

Recently, two new classes of biodegradable hydrogels have been developedfor more controlled release of a wide range of bioactive agents (e.g.,indomethacin, doxorubicin, insulin, and albumin) as well as substratesfor tissue engineering and regeneration (Kim et al., “Synthesis andCharacterization of Dextran-Methacrylate and its Structure Study bySEM,” J. Biomed. Mater. Res. 49(4):517 (2000); and Park et al.,“Biodegradable Hydrogels for Drug Delivery,” Technomic (1993), which arehereby incorporated by reference in their entirety). These newbiodegradable hydrogels are synthesized from dextran, a naturallyoccurring biodegradable, biocompatible, and hydrophilic polysaccharide,and synthetic biodegradable hydrophobic polymers, such as polylactide(“PLA”). Dextran consists primarily of 1,6-.alpha.-D-glucopyranosylresidues and has three hydroxyl groups per glucose residue that couldprovide greater flexibility in the formulation of hydrogels (Park etal., “Biodegradable Hydrogels for Drug Delivery,” Technomic (1993),which is hereby incorporated by reference in its entirety). Dextran hasbeen widely used for many biomedical purposes, such as plasma expanderand controlled drug delivery vehicle, because of its highly hydrophilicnature and biocompatibility. It is also possible to incorporatedextranase in order to facilitate biodegradation of dextran for themeeting of specific clinical needs. Both dextran and syntheticbiodegradable polyesters like polyglycolide (“PGA”), polylactide (“PLA”)or their copolymers are FDA approved raw biomaterials that arecommercially successful as synthetic, absorbable polymers for biomedicaluses, e.g., as wound closure devices. The degradation products of PGAand PLA are natural metabolites and are readily eliminated by the humanbody.

The preparation of the dextran/PLA hydrogel core of the presentinvention is based essentially based on reports and current work by theinventors of the present invention (Kim et al., “Synthesis andCharacterization of Dextran-Methacrylate and its Structure Study bySEM,” J. Biomed. Mater. Res. 49(4):517 (2000); and Zhang et al.,“Synthesis and Characterization of Novel Biodegradable IPN HydrogelsHaving Both Hydrophobic and Hydrophilic Components With ControlledSwelling Properties,” J. Polymer Chemistry 37:4554-4569 (1999), whichare hereby incorporated by reference in their entirety). In brief, thepreparation of hydrogel cores involves two major steps. The first stepis the incorporation of unsaturated groups onto dextran and PLA, withdegree of substitution (DS) used to indicate the level of suchincorporation. For example, a higher DS indicates a higher level ofunsaturated group incorporation (Kim et al., “Synthesis andCharacterization of Dextran-Methacrylate and its Structure Study bySEM,” J. Biomed. Mater. Res. 49(4):517 (2000); and Zhang et al.,“Synthesis and Characterization of Novel Biodegradable IPN HydrogelsHaving Both Hydrophobic and Hydrophilic Components With ControlledSwelling Properties,” J. Polymer Chemistry 37:4554-4569 (1999), whichare hereby incorporated by reference in their entirety). As describedearlier the DS has a profound impact on the rate and extent of diffusionof the incorporated spermiostatic agents out of the hydrogel cores. Thepurpose of the unsaturated groups is to provide photo-crosslinkingcapability between dextran and PLA. Materials suitable for use in thepresent invention include dextran of molecular weight from 43,000 to70,000 and PLA of molecular weights about 800 to 8,000, which are bothreadily available from a variety of commercial sources.

Three types of dextran derivatives and one type of PLA derivative areparticularly suitable for the core-sheath vehicle of the presentinvention. Dextran derivatives suitable include, but are not limited to,dextran-maleic acid, dextran allyl-isocyanate, and dextran-acrylate. Indextran-maleic acid; the unsaturated groups are linked to dextran viaester linkage. In the case of dextran-allyl isocyanate, the linkagesbetween the unsaturated groups and dextran are urethane bonds. Becauseof the differing sensitivities of the ester linkages (dextran-maleicacid) and urethane linkages (dextran-allyl-isocyanate) toward hydrolyticdegradation, different time-dependent swelling of the hydrogel cores forthe different types of dextran derivatives used. This provides theability to control the release rate and the extent of the impregnatedspermiostatic agents by controlling the type of dextran precursors.Dextran-maleic acid based hydrogels also have one unique advantage,i.e., the availability of controlled amounts of free —COOH groups whichcan be used to provide acidity to impede sperm motility as well as sitesfor further chemical reactions to attach desirable biochemical agents.

The next step for developing dextran-PLA hydrogel cores is the synthesisof PLA diacrylate macromers (“PLAM”) which would have the two sameunsaturated groups (i.e., acrylate) chemically introduced at the twochains ends of each PLA macromolecule.

The last step of developing hydrogel cores from both dextran derivativesand PLAM precursors involves photo-crosslinking these two precursors inthe presence of very small amounts of photoinitiators. In this laststep, fixed amounts (5-20% by weight) of a spermiostatic agent,including, but not limited to, the dihydrate form of ferrous gluconate,will be introduced into the precursor solution before crosslinking. Longwavelength UV lamp can be used for photo-crosslinking. The duration ofUV exposure can be adjusted to control the level of crosslinking, andhence the swelling and drug release profiles. Optimal concentrations ofvarious spermiostatic agents, as determined for their efficaciousrelease for 3, 7, and 28 days, are incorporated into the newlysynthesized biodegradable hydrogel cores.

The sheath material coating the hydrogel core functions to slow down thewater penetration into the hydrogel core and to retard the onset of aninitial burst release of the agents incorporated into the hydrogel core.Hence, the sheath provides a smooth. i.e., consistent, and sustainedrelease of the impregnated agents. Therefore, synthetic hydrophobicbiodegradable polymers like aliphatic polyesters and their copolymersare highly suitable materials for sheath coating. These materials areFDA approved, biocompatible, have a proven record in medicine, have apredictable biodegradation property, are hydrophobic, and arecommercially available. Biodegradable aliphatic polyester materialssuitable for use as the sheath materials in the present inventioninclude, but are not limited to PLA, poly-.epsilon.-caprolacton-e,polyglycolide, polylactide, co-polymers of polyglycolide, polylactide,and poly-ε-caprolactone, and mixtures thereof.

As noted above, a variety of hydrogel cores and sheath materials aresuitable for the fabrication of the biodegradable core-sheath matricesof the present invention. By varying the materials as well asarchitectural parameters, the present invention provides a significantlyimproved intravaginal contraceptive device that would not only be usedeasily and comfortably by women, but would also deliver a wide range ofspermiostatic and anti-infectious agents with release rates for meetingtargeted specific needs. For example, in one aspect of the presentinvention, the intended use of the device is short term, i.e., a 3 or 7day contraceptive and/or anti-infective usage. Another aspect of thepresent invention is a device that provides protection on a monthlybasis coincident with a women's menstrual cycle, i.e., for up to 28days. Thus, the device can be fabricated with more than one hydrogelcore, and/or with one or more sheath layers, each comprising a specificcombination of the materials described above as needed for the desiredapplication. Examples 7 and 8, below, illustrate the variable designprinciple of the present invention that permits the present invention tobe used for a variety of applications.

Those skilled in the art will appreciate that the newly synthesizedhydrogel precursors (i.e., dextran-maleic acid, dextran-ally isocyanate,and PDLAM), hydrogel cores, and the sheath materials are characterizedby standard polymer characterizations like FTIR, NMR, elementalanalysis, thermal and mechanical analyses, and surface morphology byscanning electron microscope. For the hydrogel cores, additionalfeatures like swelling properties, pore size, surface area, and interiormorphology are also characterized. Swelling behavior is the mostimportant factor to regulate, as it affects all other essentialproperties of hydrogels, such as permeability to bioactive agents,biocompatibility, rate of biodegradation, and mechanical properties.Mechanical properties of hydrogels will affect their structuralintegrity and dimensional stability and will give information about theability of the hydrogel to resist pressure. The pore size/volume,surface area, and cross-sectional interior morphology allow for thequalitative evaluation of the suitability of pore size and porosity ofhydrogels for drug anchorage and release. Mercury intrusion porosimeteryis used to quantify the average pore size, distribution, and pore volumeof the hydrogels. BET surface area analysis can be used to determine thesurface area of the three dimensional hydrogels. The technical aspectsof these characterizations are routine laboratory determinations, andwell within the scope and capability of one skilled in the art. Thedetailed procedures have been described by the inventors, for example inKim et al., “Synthesis and Characterization of Dextran-Methacrylate andits Structure Study by SEM,” J. Biomed. Mater, Res. 49(4):517 (2000);and Zhang et al., “Synthesis and Characterization of Novel BiodegradableIPN Hydrogels Having Both Hydrophobic and Hydrophilic Components WithControlled Swelling Properties,” J. Polymer Chemistry 37:4554-4569(1999), which are hereby incorporated by reference in their entirety.

In one aspect of the present invention the biodegradable core-sheathbiomaterials of the present invention will be cast as an intravaginalcontraceptive device in the form of a ring, or modification thereof,such as a disc. Rings have been determined to be particularlycomfortable for intravaginal application. Other physical structures mayalso be used. It will be appreciated by those skilled in the art thatthe shape of the device of the present invention may be adjusted to bestaccommodate the desired application. In one aspect of the presentinvention the device has a smooth outer surface, as shown in FIG. 1A. Inanother aspect of the present invention the device has a convolutedsurface, such as those shown in FIGS. 1B and 1C. As noted above,mechanical aspects of the device, such as surface area and interiormorphology, will determine hydrogel swelling and, ultimately, therelease rate of agents from the impregnated core. Therefore, the outersurface shape of the device can be varied along with the biodegradablematerials of the core-sheath, to optimize release rates for a givenapplication of the device.

Another aspect of the present invention is a method of contraception formammals, including, but not limited to, humans. This involvesintroducing the biodegradable, biocompatible intravaginal deliverydevice of the present invention, incorporated with an effectiveconcentration of biocompatible spermiostatic and/or spermicidal agents,into the vagina of a female mammal. Spermiostatic as used herein refersto the ability to completely retard sperm motility. Spermicidal refersto the ability to kill sperm, which may be effected physiologically whensperm have been irreversibly immobilized (Olmsted et al., “The Rate atWhich Human Sperm Are Immobilized and Killed by Mild Acidity,” FertilityAnd Sterility 73(4) 687-693 (2000), which is hereby incorporated byreference in its entirety). The spermiostatic/spermicidal aspect of thepresent invention is a provided by a three-pronged attack. Specificagents are included to: 1) reduce sperm motility to zero; 2) increasethe viscosity of cervical mucus to impede the sperm motility; and 3)sustain a pH of approximately 5.0 in the vaginal cavity to augment thetotal spermiostatic effect. Spermiostatic/spermicidal agents suitablefor the present invention include, but are not limited to, magnesiumchloride, calcium chloride, ferrous sulfate, copper sulfate, ferrousgluconate, and mixtures thereof. The use of these metallic salts asspermiostatic agents, and concentrations effective for spermiostaticefficacy are known to those skilled in the art (see, for example, U.S.Pat. No. 4,959,216 to Daunter; and Shoham et al., “Influence ofDifferent Copper Wires on Human Sperm Penetration Into Bovine CervicalMucus,” In Vitro Contraception 36(3):327-34 (1987), which are herebyincorporated by reference in their entirety).

The secretory cells of the mucosa of the cervix produce a secretioncalled cervical mucus, a mixture of water, glycoprotein, serum-typeproteins, lipids, enzymes, and inorganic salts. Females of reproductiveage secrete 20-60 ml of cervical mucus per day. Cervical mucus is morereceptive to sperm at or near the time of ovulation because it is lessviscous, and becomes more alkaline, with a pH of about 7.5-8.5, in thepresence of semen. After the ovulation, whether or not sexual relationshave occurred, the mucus becomes very thick and forms a cervical plugthat is physically impenetrable to sperm. And then the cycle repeats,with the mucus becoming less viscous as ovulation approaches and thickerafterwards.

Therefore, it follows that if viscosity of the cervical mucus wereincreased during the period of the cycle when it is less viscous, thensperm motility would be impeded. An agent suitable for increasing theviscosity of the cervical mucous in the device of the present inventionis L-ascorbic acid. It has been shown that L-ascorbic acid, morecommonly known as Vitamin C, is successful in triggering theabove-described chain of events. Ascorbic acid can act as a reducingagent on the mucopolysaccharides of the cervical mucus. It transferselectrons to the mucopolysaccharides, causing the cervical mucus tochange conformation. The open cellular structure that the mucus cellsoriginally have is subsequently closed, thus causing an increase inviscosity. This increased viscosity results in inhibited sperm motility.The increase in the viscosity of the cervical mucus induced by therelease of L-ascorbic acid from the delivery device of the presentinvention serves as the second line of resistance for the sperm to reachthe ovum.

The optimum pH value for sperm migration and sperm survival in thecervical mucus is between 7.5 and 8.5, while acid mucus immobilizessperm in the vagina, thus preventing contraception (WHO LaboratoryManual for the Examination of Human Semen and Sperm-cervical MucusInteraction, Ch. 5:51-59 (1999), which is hereby incorporated byreference in its entirety). It appears that the immobilization of spermthat occurs in the vagina at a pH of or about 5.0 may cause the death ofthe sperm by creating an environment wherein the sperm are irreversiblyimmobilized (Olmsted et al., “The Rate at Which Human Sperm AreImmobilized and Killed by Mild Acidity,” Fertility And Sterility73(4):687-693 (2000), which is hereby incorporated by reference in itsentirety). The device of the present invention functions to sustain thevaginal pH at or about a 5.0 in two ways. First, poly-amino andpolycarboxylic acid mixtures (ampholines), with a pH range of 4-6, areincorporated into the biodegradable core-sheath matrix. As these arereleased, they maintain the vaginal pH in the acidic range (at or aboutpH 5.0), even in the presence of semen. Secondly, as described ingreater detail in Example 4, the biomaterials of the hydrogel core cancontribute to an acidic environment as well. When acid-rich matricescontain, for example, maleic acid, they help sustain the vaginal pHaround 5.0 as the biomaterial is released into the vagina during theperiod of efficacy of the device.

One of the prime advantages of this unique three-pronged approach tocontraception provided by the present invention is that the combinationof methods provides for greater efficacy and dependability than othercontraceptive measures which incorporate any one, or even two, of theseapproaches in a single contraceptive. Further more, because the multipleprongs contribute simultaneously to the immobilization and death ofsperm, relatively low concentrations of spermiostatic/spermicidal agentsare needed. Furthermore, the non-hormonal, non-systemic, andbiodegradable nature of the present invention provides a method ofcontraception that can be used regularly and long-term without negativerepercussions to users' health.

Another aspect of the present invention is a method of preventinginfection in mammals including, but not limited to, humans, byintroducing the biocompatible, biodegradable device of the presentinvention in the vagina of a female mammal. This additional advantagecan be accomplished by incorporating anti-infectious agents into thedevice, with or without the spermiostatic agents. Anti-infective agentssuitable for the present invention include anti-viral agents,anti-fungal agents, antibiotics, and mixtures thereof. This is includesprophylactic treatment against sexually transmitted diseases (“STDs”)such as HIV, particularly for those in high risk populations. Dependingon the intended application of the device, the anti-infective agents ofthe present invention can be used with or without the sperm iostaticand/or spermicidal agents described above.

Another aspect of the present invention is a method of treating vaginalinfections in mammals including, but not limited to, humans, byintroducing the non-hormonal, biocompatible, biodegradable device of thepresent invention in the vagina of a female. This involves theincorporation of antibiotics, such as tetracycline, and/or anti-fungal,agents into the device, with or without the addition of spermiostatic orspermicidal agents.

EXAMPLES Example 1 Efficacy of Various Metal Salts on Sperm Motility

The effects of various concentrations of magnesium chloride, calciumchloride, ferrous sulfate, copper sulfate, and ferrous gluconate on themotility of human sperm were studied in vitro. As shown in FIG. 2,calcium chloride (CaCl.sub.2) and magnesium chloride (MgCl.sub.2) werespermiostatic at concentrations of 25 mM and 35 mM, respectively,whereas ferrous sulfate (FeSO.sub.4) completely arrested the motility ofhuman sperm at a concentration of 10 mM. Copper sulfate and ferrousgluconate were spermiostatic at concentrations of 6.25 mM and 12.5 mM,respectively, as shown in FIG. 3. 25 mM solutions of copper sulfate andferrous gluconate showed 93.3% and 97.4% immobilization of sperm,respectively, as shown in FIG. 3. 37.5 mM solutions of both reagentscompletely immobilized all the sperm, shown in FIG. 3. However, in thepresence of the dihydrate form of ferrous gluconate, the spermiostaticeffect was immediate. At lower concentrations of albumin and dextran,the spermiostatic effects were not significant; however, increasing theconcentration of albumin to 10% decreased sperm motility almost close tothat of 12.5 mM concentration of ferrous gluconate, as shown in FIG. 4.Addition of 2.5% dextran and 5% albumin to 12.5 mM ferrous gluconateshowed no enhancement of the spermiostatic effect, as shown in FIG. 4.Similarly, no additional spermiostatic effect was observed when 2.5%dextran was added to a 12.5-mM ferrous gluconate solution or when it wasadded to a 6.5-mM copper sulfate solution. However, in 20% albumin and40% albumin almost 97% of the sperm were completely immobilized. In a1.25% solution of dextran almost 95% of the sperm were immobilized.

On the basis of the above observations, the iron salt in the form offerrous gluconate, was further evaluated as the spermiostatic agent.Ferrous gluconate is not toxic, is biocompatible, and is used as anutritional iron supplement. Iron promotes lipid peroxidation. Lipidperoxidation is a type of cellular damage involving the formation ofoxygen free radicals, such as super-oxide anion (Hong et al., “Effect ofLipid Peroxidation on Beating Frequency of Human Sperm Tail,” Andrologia26:61-65 (1993); Aitken et al., “Relationship Between Iron-CatalyzedLipid Peroxidation Potential and Human Sperm Function,” J. Reproductionand Fertility 98:257-265 (1993); and Calamer et al., “Effect of LipidPeroxidation Upon Human Spermatic Adenosinetriphosphate (ATP).Relationship With Motility, Velocity and Linearity of the Spermatozoa,”Andrologia 21(1):48-49 (1988), which are hereby incorporated byreference in their entirety). Radicals are extremely unstable andunfavorable to the lipid bilayer of a cell resulting in cell damage. Thelipid peroxidation process, as shown below, is initiated in humanspermatozoa when intracellular production of reactive oxygen speciesoverwhelms the antioxidant defense system, namely, superoxide dismutase(SOD), used by the cell. Human spermatozoa are enriched with unsaturatedfatty acids and fatty acids are particularly susceptible to lipidperoxidation. Sperm are thus predisposed to peroxidative damage. Thisreaction occurs when lipid peroxides in the bilayer of sperm tails areexposed to ferrous ion resulting in the propagation of lipidperoxidation, which leads to a continuous formation and decomposition oflipid peroxides. Eventually, this causes structural damage, a decline inmetabolic activity, and spermiostatic effects in sperm cells. Ferrousgluconate targets sperm tail and causes lipid peroxidation as shownbelow. 1

Example 2 Effect of Various Concentrations of Ascorbic Acid on theViscosity of Human Cervical Mucus

At the commencement of the menstrual cycle, cervical mucus has a tighthoney-comb cellular structure with a channel diameter of 2-6 m.mu.m,which forms an impenetrable barrier to sperm. At midcycle, the channeldiameter is 30-35 m.mu.m in order to allow the sperm to pass. At theluteal phase, the cellular structure again contracts to 2-6 m.mu.m, andthe mucus becomes more viscous (WHO Laboratory Manual for theExamination of Human Semen and Sperm-cervical Mucus Interaction, Ch.5:51-59 (1999), which is hereby incorporated by reference in itsentirety). L-ascorbic acid is an antioxidant, transfers electrons, andacts as a reducing agent for disulfide (—S—S—) bonds ofmucopolysaccharides of glycoproteins forming the cervical mucus, thuschanging the mucus from open cellular structure found at midcycle of themenstrual period to the closed cellular structure to form animpenetrable barrier for sperm. The effect on L-ascorbic acid was testedin vivo using cervical samples collected from female volunteers duringtheir fertile phase.

To collect cervical mucus from female volunteers, the cervix is exposedwith a speculum, and the external os is gently wiped with a cotton swabto remove the external pool of vaginal contaminants. Cervical mucus isaspirated with a needleless tuberculin syringe. The pH of the collectedcervical mucus is determined with pH paper (range 6.4-8.0). The optimumpH value for sperm migration and survival in the cervical mucus isbetween 7.0 and 8.5. Acidic mucus immobilizes spermatozoa (WHOLaboratory Manual for the Examination of Human Semen and Sperm-cervicalMucus Interaction, Ch. 5:51-59 (1999), which is hereby incorporated byreference in its entirety). Mucus is preserved in the originaltuberculin syringe and covered with parafilm to avoid dehydration. Thesamples are preserved in a refrigerator at 4.degree. C. for a period notexceeding 5 days. Usually the mucus specimens are utilized within 2 daysof collection. Various dilutions of L-ascorbic acid are mixed with anappropriate aliquot of mucus and incubated for 30 minutes at 37.degree.C. and the cervical mucus consistency is determined. Cervical mucusconsistency is scored as recommended by WHO (WHO Laboratory Manual forthe Examination of Human Semen and Sperm-cervical Mucus Interaction, Ch.5:51-59 (1999), which is hereby incorporated by reference in itsentirety) as follows. Various parameters of cervical mucous consistencyof untreated and treated mucus can be compared to determine the optimumamount of ascorbic acid needed to achieve desired viscosity of themucus.

1 Score Viscosity 0=Thick, highly viscous, premenstrual mucus 1=Mucus ofintermediate viscosity 2+=Mildly viscous 3=Watery, minimally viscous,mid-cycle (pre-ovulatory mucus)

A second parameter of the cervical mucus examined is known as thespinnbarkeit of the mucus. Spinnbarkeit is the term used to describe thefibrosity, the threadability, or the elasticity of cervical mucus.Cervical mucus placed on a microscope slide is touched with a coverslip, or a second slide held crosswise, which is lifted carefully. Thelength of the cervical mucus thread stretches in between the twosurfaces is estimated in centimeters and scored as follow (WHOLaboratory Manual for the Examination of Human Semen and Sperm-cervicalMucus Interaction, Ch. 5:51-59 (1999), which is hereby incorporated byreference in its entirety):

2 Score Length (in cm.) 0=less than 1 cm 1=1-4 cm 2=5-8 cm 3=9 cm ormore

The effect of L-ascorbic acid on ferning was also tested. Ferning refersto the degree and pattern of crystallization of the mucus observed whendried on a glass surface. Ferning is due to decreased levels of salt andwater interacting with glycoprotein on the mucus. Ferning is increasedin capacity as ovulation approaches. To test for ferning, cervical mucusis laced in a glass slide, air-dried, and viewed under a lightmicroscope. Ferning is scored as follows:

3 Score Description of ferning 0=No crystallization 1=Atypical fernformation 2=Primary and secondary stems, ferning 3=Tertiary andquaternary stems, ferning

For the purpose of the present invention, ascorbic acid is oxidized todehydroascorbic acid and the latter is coupled with2,4-dinitrophenylhydrazine. The coupling reaction forms the2,4-dinitrophenylosazone of dehydroascorbic acid, a light-browncrystalline compound. When treated with 85% H.sub.2SO.sub.4, the osazoneis rearranged to form a reddish colored compound, which absorbsmaximally at 500 to 550 nm. It is a highly stable product under theconditions used and is well suited to colorimetric measurement.

Reagents for this include: trichloroacetic acid solutions, 6% and 4%;2,4-Dinitrophenylhydrazine reagent. A stock solution of ascorbic acid ismade by dissolving 50 mg of ascorbic acid of the highest purity in 100ml of 0.5% oxalic acid. Store at 4.degree. C.

To make a standard solution of dehydroascorbic acid, place 2 ml of theascorbic acid stock solution in a 100 ml volumetric flask and make up tovolume with 4% trichloroacetic acid solution. This solution is oxidizedby adding 1 teaspoonful or (1 g) of acid-washed Norite per 50 ml,shaking thoroughly, and filtering through Whatman No. 42 filter paper.One ml of this solution contains 10 .mu.g of dehydroascorbic acid. Storeat 4.degree. C.

To prepare solution filtrate: to one volume of solution, add 19 volumesof 4.0% trichloroacetic acid. This dilution will serve for a range of 1to 300 mg of ascorbic acid per liter of solution.

The procedure is as follows. Place 4 ml of Norite filtrate of unknownsin each of two matched photoelectric calorimeter tubes. Place in anothermatched colorimeter tube 4 ml of the dehydroascorbic acid standardsolution (10 .mu.g per ml). To the standard tube and the tube containingNorite filtrate, add 1 ml of 2,4-dinitrophenylhydrazine reagent. Theother tube containing Norite filtrate is used as a control, no reagentbeing added to the tube at this time. Place the three tubes in aconstant temperature water bath at 37.degree. C. Keep the tubes immersedin the bath for exactly 3 hours. Remove and place them in a beaker ofice water containing generous quantities of ice. To each of the threetubes, while in the ice water bath, add slowly 5.0 ml of 85%H.sub.2SO.sub.4. Finally, to the control tubes, add 1 ml2,4-dinitrophenylhydrazine reagent. The tubes are shaken under the icewater to achieve complete mixing and are then placed in a rack. After 30minutes, wipe the tubes dry and clean and record the absorption in acalorimeter using, a 540 m.mu. filter. To take the reading, use thecontrol tube to set the colorimeter at 100% transmittance or zeroabsorbance (Roe, in Seligson, ed., Standard Methods of ClinicalChemistry, Vol. 3, New York: Academia Press, p. 35 (1961), which ishereby incorporated by reference in its entirety). The cervical mucousscores from four samples tested at concentrations of ascorbic acid from0-10% are shown below in Table I.

TABLE 1 CERVICAL MUCUS SCORES AT VARIOUS CONCENTRATIONS OF ASCORBIC ACIDFOR FOUR DIFFERENT SAMPLES 0% 0.31% 0.63% 1% 1.25% 2.50% 5% 10% Jun. 22,2000 pH 4 ± .71 5 ± .9  4 ± .9  4 ± .53 3 ± .38 3 ± .58 3 ± .75  2 ±1.13 Quantity .3 ± .53  .3 ± .67  .3 ± .67  .3 ± .67  .3 ± .67  .3 ±.67  .3 ± .67  .3 ± .67  Viscosity 0 3 ± .79 1 ± .81 1 ± .75 1 ± .95 2 ±.61 2 ± .52 1 ± .69 Ferning 3 ± .38 2 ± .86 0 ±  2 ± .82 0 0 0 1 ± .53Spinnbarkeit 1 ± .79 0 1 ± .49 1 ± .51 1 ± .51 1 ± .14 1 ± .35 1 ± .26Cellularity 3 ± .38 2 ± .86 0 2 ± .82 0 0 0 1 ± .53 TOTAL   7.3   7.3  2.3   6.3   2.3   3.3   3.3   4.3 Jun. 23, 2000 pH 8 ± .71 2 ± .9  2 ±.9  3 ± .53 3 ± .38 3 ± .58 3 ± .75  2 ± 1.13 Quantity .2 ± .53   .2 ±.067  .2 ± .067  .2 ± .067  .2 ± .067  .2 ± .067  .2 ± .067  .2 ± .067Viscosity 2 ± 1  3 ± .79 2 ± .81 2 ± .75 3 ± .95 0 2 ± .52 2 ± .69Ferning 3 ± .38 0 0 0  ± 0 0 1 ± .53 Spinnbarkeit 2 ± .79 1 ± .35 1 ±.49 1 ± .51 1 ± .51 1 ± .14 0 1 ± .26 Cellularity 2 ± .68 2 ± .58 0 0 01 ± .49 0 1 ± .51 TOTAL   9.2   6.2   3.2   3.2   4.2   2.2   2.2   5.2pH 4 ± .71 4 ± .9  4 ± .9  4 ± .53 4 ± .38 2 ± .58 2 ± .75  2 ± 1.13Quantity .15 ± .53  .15 ± .067  .15 ± .067  .15 ± .067  .15 ± .067  .15± .067  .15 ± .067  .15 ± .067  Viscosity 0 2 ± .79 1 ± .81 2 ± .75 1 ±.95 1 ± .61 2 ± .25 1 ± .69 Ferning 3 ± .38 0 0 0 0 0 0 0 Spinnbarkeit 1± .79 0 1 ± .49 1 ± .51 0 1 ± .35 1 ± .26 Cellularity 3 ± .68 1 ± .58 1± .61 0 1 ± .53 1 ± .49 0 1 ± .51 TOTAL 7   3.15   3.15   3.15   2.15  2.15   2.15   3.15 pH 7 ± .71 4 ± .9  5 ± .9  4 ± .53 4 ± .38 4 ± .582 ± .75  3 ± 1.13 Quantity 0.2 ± .53   .2 ± .067  .2 ± .067  .2 ± .067 .2 ± .067  .2 ± .067  .2 ± 0.67  .2 ± .067 Viscosity 3 ± 1  2 ± .79 3 ±.81 2 ± .75 3 ± .95 2 ± .61 2 ± .52 0 Ferning 3 ± .38 0 3 ± .86 3 ± .82 2 ± 1.13 1 ± .82 0 0 Spinnbarkeit 3 ± .79 1 ± .35 1 ± .49 1 ± .51 1 ±.51 1 ± .14 1 ± .35 0 Cellularity 2 ± .68 0 0 0 1 ± .53 1 ± .49 1 ± .660 TOTAL  11.2   3.2   7.2   6.2   7.2   5.2   4.2   0.2 *pH NOT INCLUDEDIN TOTAL

It is evident from the cervical mucus score that overall viscosity ofthe mucus increased in direct relationship with increasingconcentrations of L-ascorbic acid from 0.31% to a range of 1-2.5%. Asshown in Table 2, the daily eluates for twelve consecutive days ofhydrogel matrix DA containing L-ascorbic acid also increased theviscosity of the cervical mucus equivalent to that of normal follicularand luteal phases.

TABLE 2 CERVICAL MUCUS SCORE OF THE DAILY ELUATES OF THE MATRIX May 10,May 11, May 12, May 13, May 14, May 15, May 16, May 17, May 18, May 19,May 20, May 21, Parameter 2000 2000 2000 2000 2000 2000 2000 2000 20002000 2000 2000 pH 7 7 7 7 7 5 7 3 4 5 4 6 Viscosity 0 0 0 1 1 0 0 1 0 12 2 Ferning 1 0 0 2 2 0 0 0 0 0 0 0 Spinnbarkeit 0 0 1 1 0 0 1 1 0 1 1 1Cellularity 2 2 2 2 2 0 0 0 0 0 0 0 TOTAL 3 2 3 6 5 0 1 2 0 2 3 3 NormalAverage values (number of subjects) of the total cervical mucus score(Viscosity, Ferning, Spinnbarkeit and Cellularity) Follicular Phase 3.6(11) Midcycle 13.1 (3) Luteal Phase 4.4 (6)

Example 3 Three Generations of Biodegradable Matrices and theirControlled Release of Ferrous Gluconate

Three generations of biodegradable matrices impregnated with dihydrateferrous gluconate were designed and tested for release profiles andefficacy on sperm motility.

The first generation matrix tested consisted of an aliphatic polyestercopolymer from PLA and poly (F-caprolactone) containing 24% ferrousgluconate by weight. Aliphatic polyesters have a proven record in thebiomedical field, predictable biodegradation properties, FDA approval,and commercial availability. The first generation matrix was thesimplest design for determining whether the concept of controlledrelease of spermiostatic agents from biodegradable substrates would befeasible and warrant additional studies.

The release data from the first generation matrix prompted thedevelopment of a sandwich design, which was used for the secondgeneration matrix. The purpose of this sandwich configuration was toenhance the controlled release of the impregnated spermiostatic agent,particularly after the initial release. The center layer of the sandwichwas a copolymer of PLA and Poly(.epsilon.-caprolactone) containing 38.7%of ferrous gluconate. The top and bottom layers werepoly(.epsilon.-caprolactone) homopolymer (“PCL”) containing 21.5%ferrous gluconate by weight.

Since the release of ferrous gluconate from the 1st and 2nd generationbiodegradable matrices showed a relatively short lived 24 hour burstrelease profile and the matrices did not have sufficient ferrousgluconate remaining as the reservoir for subsequent sustainedspermiostatic activity, a third generation biodegradable matrix wasdesigned. This third generation employed a new biodegradable core andsheath design concept to provide more sustained and smooth release overa long period. The hydrogel gel was based on a new technology (Park etal., “Biodegradable Hydrogels for Drug Delivery,” Technomic (1993),which is hereby incorporated by reference in its entirety). This innerhydrogel core was covered by biodegradable sheath. The objective of thehydrogel core is to provide sustained release of the contraceptiveagents during the late stage as well as to compensate for the decliningconcentration of the agents released from the sheath materials in theearly stage. The intended functions of the sheath materials are threefold. First, they would retard the onset of swelling of the hydrogelcore during the early stage of application and hence preserve itsimpregnated contraceptive agents for later stage release. Second, thesheath materials could also restrict the well-known burst release ofdrugs from the hydrogel core so that it would “smooth out” the releaseof the incorporated agents from the hydrogel core. Thirdly, the sheathmaterial will be the source of ferrous gluconate for initial stagerelease. Since the sheath materials would be used to release ferrousgluconate in the initial stage and to delay and contain the release ofthis agent from the core, synthetic biodegradable biomaterials havinggood hydrophobicity and/or tight mesh structure were used. The coresheath design was expected and was indeed observed to provide sustainedrelease of the incorporated spermiostatic agent over a desired period.By using a combination of a variety of core-sheath design concepts, suchas multicore-sheath design, a wide range of release profiles could begenerated and tailored accordingly to specific clinical needs. This caninclude variable terms of use, for example, for short term contraceptiveusage for 3-7 days, or full-cycle (28 day) anti-viral, anti-SST andcontraceptive protection.

The biodegradable hydrogel cores used in the third generation werethree-dimensional hydrogel networks consisting of dextran-PLA (Park etal., “Biodegradable Hydrogels for Drug Delivery,” Technomic (1993),which is hereby incorporated by reference in its entirety). Both dextranand PLA are FDA-approved biomaterials and hence would ensurebiocompatibility, contain the cost of development, and bring theproducts to clinical trials at a faster pace. The technology of thepresent invention combines the merits of natural biodegradable polymerslike dextran with synthetic biodegradable polymers like PLA into asingle entity (via chemical crosslinking) so that there would be nophase separation, resulting in better and more predictable release ofthe incorporated biochemical agents. By controlling the compositionratio of dextran (as hydrophilic component) to PLA (as hydrophobiccomponent), a wide range of swelling properties (i.e., a wide range ofdrug release profiles), differing degrees of hydrophobicity, and a threedimensional porous network having pore sizes between 0.1 .mu. and 600.mu. can be achieved.

Five versions (A, B, C, D, and DA) of the third generation device weredeveloped. They varied in the number and type of Sheath materials,concentration of the impregnated ferrous gluconate, and use ofL-ascorbic acid. The same hydrogel core was used for all five versions.The compositions of samples A, B, C, D, and DA are as follows.

Sample A contained a core made of Dextran-Al hydrogel, with 2% ferrousgluconate by weight. The inner first sheath was made of the copolymer of.epsilon.-caprolactone and L-lactide containing ferrous gluconate (73.8%by weight of the polymer). The second sheath consisted ofpoly-.epsilon.-caprolactone containing predetermined amounts of ferrousgluconate.

Sample B had the same hydrogel core as Sample A with 2% ferrousgluconate by weight. The inner first layer containedpoly-.epsilon.-caprolactone/poly-L-lactide copolymer containingpredetermined amounts of ferrous gluconate. The second layer waspoly-.epsilon.-caprolactone homopolymer containing predetermined amountsof ferrous gluconate. The third layer was made up ofpoly-.epsilon.-caprolactone/poly-L-lactide/polyethylene glycolcopolymer, without ferrous gluconate.

Sample C had the same hydrogel core as Sample A containing 2% ferrousgluconate by weight. The inner first sheath waspoly-.epsilon.-caprolactone/poly-L-lactide copolymer containingpredetermined amounts of ferrous gluconate. The second inner sheath wasof poly-.epsilon.-caprolactone-homopolymer containing predeterminedamounts of ferrous gluconate.

Sample D had the same hydrogel core as Sample A containing 2% dihydrateferrous gluconate by weight. This core material was coated by thefollowing four layers of biodegradable polymers. The first layer waspoly-D-L-lactide macromer impregnated with predetermined amounts offerrous gluconate. The second layer waspoly-.epsilon.-caprolactone/poly-L-lactide/polyethylene glycol copolymercontaining predetermined amounts of ferrous gluconate. The third layerwas poly-.epsilon.-caprolactone/pol-y-L-lactide copolymer impregnatedwith predetermined amounts of ferrous gluconate. The fourth layer alsocontained poly-.epsilon.-caprolactone/po-ly-L-lactide copolymer but wasnot impregnated with ferrous gluconate.

The ferrous gluconate release profiles from the first four of the thirdgeneration samples are shown in FIGS. 5-8. Sample A, shown in FIG. 5,and Sample B, shown in FIG. 6, showed efficacious spermiostatic activityfor 8 days. Thus, these two samples are candidates for contraceptivedevices of one-week duration; however, they are not sufficient forlonger sustained release for the 28-day period.

Sample C, shown in FIG. 7, and Sample D, shown in FIG. 8, exhibitedacceptable daily release rates of ferrous gluconate and withapproximately 33% and 42% biodegradability of the matrices,respectively, for a period of 16 days. Release rates are shown in Table3 as a change in the weight of the respective matrix. However, Sample Dshowed the best sustained controlled release among all the threegenerations of matrices and appears to have the potential for deliveringefficacious spermiostatic agents for longer periods than other matricestested.

TABLE 3 CHANGE IN THE WEIGHT OF THE MATRICES C AND D Initial weightFinal Weight Sample (gm) (gm) Differences (gram) Days Sample C 0.5541(gm) 0.375 (gm) 0.179 (gm) 16 Sample D 0.5406 (gm) 0.306 (gm) 0.234 (gm)16

Sample DA contained the same hydrogel core as Sample D containing 2%ferrous gluconate by weight. In addition, the hydrogel core consisted ofpredetermined amounts of L-ascorbic acid, photoinitiator2,2-dimethoxy-2-phenyl acetophenone, and N,N′-dimethyl formamide. Theinner first layer was composed of poly-D-L-lactide macromer, ferrousgluconate, L-ascorbic acid, photoinitiator 2,2-dimethoxy-2-phenylacetophenone, and NN′-dimethylformamide. The second inner sheathcontained lactide/caprolactone/ethylene oxide copolymer andpredetermined amounts of ferrous gluconate, L-ascorbic acid, andchloroform (6% by weight). The third layer was made up oflactide/caprolactone copolymer, ferrous gluconate, L-ascorbic acid, andchloroform, again 6% by weight. Sample DA was coloaded with both ferrousgluconate and ascorbic acid. The daily eluates from matrix DA wereanalyzed for ferrous gluconate and ascorbic acid as described earlierand shown in FIG. 9 and FIG. 10, respectively. The spermiostatic effectand effect on the increase in the viscosity of the cervical mucus isshown in Table 2. The spermiostatic activity was tested for 11 days andincrease in the viscosity of the cervical mucus was tested for 15 days.As shown in FIG. 11, the spermiostatic effect was achieved within 10seconds and the pH of eluates was stabilized between 5 and 6, as shownin FIG. 12. It is clearly indicated that a combination of iron andascorbic acid has the potential of being an effective spermiostaticagent.

Example 4 Testing of Acidity of Acid-Rich Biodegradable Biomaterials

The objective of this example was to determine whether, in addition tobeing the vehicle for controlled delivery of spermiostatic agents, theacid-rich biodegradable biomaterials of the present invention could alsoserve as an acid donor to make the surrounding medium acidic forenhancing the spermiostatic activity. The numbers of the free —COOHgroups could also be modified to provide the preferred acidicenvironment by changing the reaction conditions for augmenting thespermiostatic effect. In this preliminary study, a fixed amount ofdextran-maleic acid hydrogel and a co-poly(ester amide) were separatelyimmersed in distilled water and the pH of the water was measured for anextended period. Table 4 summarizes these findings.

TABLE 4 CHANGE OF pH OF AQUEOUS MEDIUM IN THE PRESENCE OF ACID-RICHBIODEGRADABLE BIOMATERIALS Immersion Dextran-Maleic Acid Co-Poly(ester-amide) Time (Days) pH pH 0 6.20 6.28 1 4.33 5.31 3 4.39 4.41 84.42 4.31 15 5.20 4.17

These data illustrate that the biodegradable biomaterials of the presentinvention could be used not only as the hydrogel core and/or sheathmaterials for this proposal, but could also have the advantage ofproviding an adequate acidic environment for impeding sperm motility.

Example 5 In Vitro Rabbit Sperm Immobilization Studies

The spermiostatic effect of the elutes of hydrogel DA impregnated withferrous gluconate and ascorbic acid on rabbit sperm in7 vitro wasexamined. Due to the necessity of using rabbit sperm on the same daythat the ejaculates are collected, daily eluates from five consecutivedays were analyzed. Rabbit semen was diluted three-fold with phosphatebuffered saline to achieve counting efficiency of approximately50.times.10.sup.6 per ml. Twenty .mu.l of eluate was mixed with 20 .mu.lof the diluted semen. In Day 1 and Day 3 eluates with up to 1:3dilution, all sperm were immobilized instantaneously with shakingmovement. Day 4 eluates caused immobilization with shaking or shivering,but no movement. Day 5 eluates showed slower immobilization andincreased number (up to 10%) of shaking or shivering sperm.

Example 6 Evaluation of the Effect of the Contraceptive Core-SheathMatrices on Rabbit Sperm Function In Vivo

On Day 1, female rabbits in estrus were selected using teaser males. Thehydrogel impregnated with contraceptive core-sheath matricescorresponding to matrix sample DA, described above, was inserted intothe anterior vagina within a wide insemination pipette at 11 AM. Theestrus female was mated some 6 hours later to a male of known fertility(at about 5 PM) and then given 50 IU human chorionic gonadotrophin (hCG)intravenously via ear vein to ensure ovulation.

A functional population of spermatozoa sufficient to ensurefertilization was established within the rabbit cervix by 5 minutesafter mating/ejaculation as described by Bedford, “The Rate of SpermPassage Into the Cervix After Coitus in the Rabbit,” J. Reprod.; Fertil.25:211-218 (1971), which is hereby incorporated by reference in itsentirety. However, for the purposes of this study a post-coitalevaluation of the residual vaginal sperm population in females with thecontraceptive gel was conducted approximately 30 minutes afterejaculation. This was accomplished by insertion of an artificialinsemination pipette as far as the cervix, in the manner used forartificial insemination, and then aspiration of anterior vaginal contentwhich was examined under phase microscope to determine the percentageand quality of sperm motility. All sperm appeared 100% immobilized.

On Day 2, the same female was again mated, and a post-coital examinationof the vaginal content revealed 100% immobilized (dead) sperm. The pH ofthe vaginal canal after coitus was 5.0. No irritation of the vaginaltissue was detectable. Sperm retrieved from the vaginal canal wereplaced in modified human tubal fluid (Irvine Scientific, Santa Ana,Calif.) buffered with HEPES and incubated at 37.degree. C. for purposesof rejuvenation. No sperm were capable of being rejuvenated, indicatingcomplete sperm immobilization was achieved by the contraceptivecore-sheath matrix.

In rabbits, a pregnancy can be palpably detected at ten days, thereforefrom Day 11 of the study forward, the mated female was checked forpregnancy. Up to and including 21 days after the initial mating nopregnancy occurred, indicating the contraceptive efficacy of the matrixcontaining the sperm iostatic/spermicidal agents of the presentinvention.

Example 7 A Two-Hydrogel Core Device

In this design, there will be two hydrogel cores separated by severallayers of biodegradable hydrophobic polymer sheath. The objective of theinner core is to facilitate the sustained release of the impregnatedagents during the late stage of application. The outer core will be usedto improve the release of the spermiostatic agents in the middle stageof application. The inner and outer cores can be made from either thesame or different hydrogel precursors or from the same hydrogelprecursors, but with different DS, i.e., different tightness of thethree-dimensional network structure. A prolonged and more sustainedrelease will require a tighter three dimensional network structure,i.e., higher DS. The insulating materials that separate the two coreswill be the sheath materials described above. These sheath materialswill have the spermiostatic agents impregnated at differentconcentrations. There will be several options for the number of sheathlayers and their thickness. Fewer and/or thinner-sheath layers can beexpected to accelerate the release of the incorporated spermiostaticagents.

Example 8 A Five-Hydrogel Core Device

In this design, the desirable release duration is divided into finer,more discrete periods, i.e., early, early-middle, middle, middle-late,and late stages. This discrete division of the release periods providesfor the fine-tuning of the release profiles to permit even smoother andmore sustained release of the spermiostatic, spermicidal andanti-infective agents incorporated into each hydrogel core. Theinnermost layer will be for the late stage release; the next innermostlayer will be for the riddle-late stage and so on, with the outermostlayer for the early stage release. These hydrogel cores will beseparated by sheath materials in the same manner as the two-hydrogelcore design.

Although preferred embodiments have been depicted and described indetail herein, it will be apparent to those skilled in the relevant artthat various modifications, additions, substitutions, and the like canbe made without departing from the spirit of the invention and these aretherefore considered to be within the scope of the invention as definedin the claims which follow.

1-32. (canceled)
 33. An intravaginal contraceptive device, comprising: abiocompatible support structure, configured to be inserted into awoman's vagina and to safely remain therein for three days; the supportstructure comprising a non-hormonal contraceptive composition, thesupport structure and composition adapted to release effective amountsof the composition during the three days; the contraceptive compositioncomprising a sperm-mobility reducing effective amount of ferrousgluconate, ferrous sulfate or copper sulfate and combinations thereof; acervical mucus viscosity increasing effective amount of ascorbic acid;and a pH buffering effective amount of ampholines, the compositionformulated to maintain a vaginal pH at a spermiostatic level.
 34. Thedevice of claim 33, wherein the composition comprises ferrous gluconate.35. The device of claim 33, wherein the ampholine component comprisespoly-amino acids or polycarboxylic acids or combinations thereof. 36.The device of claim 35, wherein the composition comprises ferrousgluconate.
 37. The device of claim 33, wherein the composition iseffective to maintain the pH in the vaginal cavity at about
 5. 38. Thedevice of claim 33, wherein the composition is effective to maintain thepH at about 3.5 to 5.5.
 39. The device of claim 33, wherein thecomposition comprises magnesium chloride or calcium chloride.
 40. Thedevice of claim 33, wherein the support structure comprises poly-DLlactide.
 41. The device of claim 33, wherein the support structurecomprises hydrogel material.
 42. The device of claim 33, wherein theampholine component comprises an acid-rich polymer.
 43. The device ofclaim 33, wherein the support structure has an annular shape.
 44. Thedevice of claim 33, wherein the composition is formulated to prevent thepH in a vagina from increasing in the presence of semenal fluid.
 45. Thedevice of claim 33, wherein the support structure with the compositiondisposed therein is constructed and formed of materials effective toprovide sustained release of said effective amount of the compositionfor 7 days.
 46. The device of claim 33, wherein the support structurewith composition disposed therein is constructed and formed of materialseffective to provide sustained release of said effective amount of thecomposition for 16 days.
 47. The device of claim 33, wherein the supportstructure with composition disposed therein is constructed and formed ofmaterials effective to provide sustained release of said effectiveamount of the composition for 28 days.
 48. The device of claim 33,wherein the device comprises effective amounts of material to maintain apH of about 5-6 in a vagina during the sustained release of saidcomposition, in the presence of semenal fluid.
 49. The device of claim36, wherein the device is effective to result in maintain a pH of about3.5 to 5.5.
 50. The device of claim 36, wherein the support structurewith composition disposed therein is constructed and formed of materialseffective to provide sustained release of said effective amount of thecomposition for 28 days.
 51. The device of claim 50, wherein the deviceis effective to maintain a pH of about 3.5 to 5.5.
 52. The device ofclaim 51, including poly-amino acids, polycarboxylic acids orcombinations thereof.